Assuming that is as strange as assuming that the only reason people get professional massages is because they can't find a boyfriend/girlfriend to do it for them.
The guys I know who go to prostitutes don't do it because they can't get laid conventionally. They do it because it's no muss, no fuss. A simple transaction after which they don't have to worry about the other person's feelings or anything like that, and because it's a sure thing on a short time scale, rather than a long time investment that may or may not pay off.
Now, I happen to think the actual intimacy is the best part of sex, but not all guys feel that way. That doesn't mean that they're desperate or socially rejected.